Drying apparatus for gelatin carbon tissue



June 10, 1930. v T. CHESTER 1,762,910

DRYING APPARATUS FOR GELATIN CARBON TISSUE Q File'd Aug. 1, 1928INVENTOR ATTORNEY Patented 10, 1930 UNITED- TATE FATE-M OFFICE momscnnsmm, or rrrrsnunez, rmsnvm Y DRYING APPARATUS FOR GEIATIN CARBONTISSUE D Application. filed. August 1, 1928. Serial 1W0." 88,817.

This invention relates to drying apparatus for gelatin carbon tissues,employed in the illustrating process lmown a's rotogravure.

6 The roto'gravure process, as do most of the processes pertaining tothe rinting arts, includes a large number of elicate operations a'ndinvolving the use of the fragile carbon tissues to which reference hasbeen 10 made. Such tissues are well known in the art and comprise thinpaper backingscoated with gelatin emulsions, and the rocess of theiremployment is outlined as ollows:

The tissue as received is not sensitized to light and must be preparedfor use by subjection' to a sensitizing potassium' bichro- .mate .bath.The tissue is next squeegeedface down on a polished metal ferrotype Iplate on whichit is dried. Thereafter the 0 tissue is peeled from theplate and stored in light-proof means until it is to be used.

Ordinarily several sheets of tissues are so.

sensitized and prepared at once and preferably a relatively short timebefore their 2 use is intended. 1

When one of the sensitized tissue sheets is to be employed it is printedupon by exposure to light through a photographically obtained positive,developed, fixed and. washed as is usual in the photographic art. Nextcomes the process wherein the tissue sheet is wrapped-and squeegeedaround ,a polished copper cylinder, which is then subected to a hotwaterbath for a eriod of indeed, remove part of the gelatin thereof dependentupon the, pattern of the ositive. The cylinder is then dried and subected to H a ferric etching solution which lightly etches timesufiicient to: .disintegrate t e paperinto the exposed surface portionsof the cop ments are to be printe are of considerable area, running innewspa r work to around 46" x 29"; and the etc 'ng is very light.Further, competition among publishers dictates an extremely high qualityof work, and it will beappreciated that very great care must be employedthroughout the progress of the carbon tissue. i

Perhaps the most fruitful and least understood souree of inaccuracies inthe product 7 is in the drying of the tissue on the ferrotype plates,the general practice in the art heretofore being to use the greatestcare and skill in otherwlse handling the tissue sheetbut, inconsistentlyenough, to dry the same by standin its ferrotype plate on edge anddirecting t ereagainst the breeze from an electric fan. The result isinvariably that some ,of the water with which the 'aper is, saturatedworks down by avity e ecting a distortion in the tissue. oreover whereat-' mospheric or room air is employed, in winter such air is usually sodr that the tissuei'stoo rapidly dried, out wh1le in summer such air isusually too warm and too humid; in either caseproducing still furtherdistortion of the tissue. This method also obviously subjects the tissuebacking to all the dust and forei matter in the atmosphere which laterfin s its way to produce relatively minute but distinct inaccuracies inthe copper printing cylinder. 7

My invention is directed toward the prociess of drying the tissue on theferrotype plates, and involves 'so controlling the conditions of thedrying operation that the same is independent of weatheror roomconditions and results in a very substantial super-' iority and exactuniformlty of product.

To this end I provide a chamber in which. the tissue is dried, andarrange'for circulatin the dry medium, such as air, through thecilamber, and forconditioning the me dium before the tissue sheets areexposed thereto, preferably recirculating the same so that outside dustis not accumu ated thereby. Further, in order that a number offerrotypeplates with their sheets of tissue may be accomodated, and that eachsheet may receive an even distribution of air over its surface, and thatthe air may find free exit from the sheets, I provide in the chamberthrough which the air is circulated, a rack of shelves of novelconstruction as will appear more in detail hereinafter.

The exact nature of the invention to ether with further objects andadvantages t ereof will be apparent from the following description,taken in connection with the accompanying drawings, in which Fig. 1 is aplan view of apparatus in which my invention is incorporated; Fig. 2 isavertical section partly diagrammatic but generally in the plane of line22, Fig. 1; Fig. 3 is i a detailed vertical section as in the plane 33,Fig. 1; and Fig. l is a detail in perspective of a corner of one of theshelves employed.

Vifith reference now to the drawings, I provide a rack 1 having a numberof horizontal rectangular shelves 2 supported as by means of the cornerposts 3, each shelf being of suficient supporting area to receive andsupport a ferrotype plate bearing a sheet of gelatin carbon tissue.

Each of the shelves 2 is hollow, as of sheet metal, and is really an airbox, is provided as on its under side as indicated Fig. 4, with a numberof relatively small and closely spaced perforations 4, and has on oneedge one or more connections 5 whereby a drying fluid may be supplied tothe shelf air box.

I arrange the rack 1 within an enclosure having its left and right sidewalls 6 and 7 and rear wall 8 well spaced from the rack. Above the rackI arrange a container or, as indicated in the drawings and by thepartitioning members 9, 10 and 11, a compartment or subenclosure.Extending downwards of the right-hand wall 10 and between the rear wallof the compartment and the front wall thereof is a partition 12 havingopenings 13 corresponding with the connections 5' of the shelves 2, theconnections 5 being secured in these openings as indicated Fig. 2. Thespace bounded by the walls 7 8 and partitions l0 and 12 thus forms achamber B through which access may be had with the chamber A in whichthe rack 1 is located, by way of the openings 13, connections 5, thehollows of the shelves 2 and the perforations 4, free exit from betweenthe shelves being had on all sides thereof.

Upper and lower doors 14 and 15 are-provided as indicated Fig. 3, whichtogether with the parts already described, substantially form of theinterior of the enclosure, the chambers A and B as set forth and thechamber 0 in the upper portion thereof.

A blower 16 as of the centrifugal type indicated, and driven by a motor17 and which may be located above the enclosure is provided, and bymeans of the fan outlet duct 18 is arranged to deliver a drying mediumsuch as air, through an inlet opening 19 to the chamber B. i

The up er portion of the chamber A lying between t e wall 6 andpartition 9 has an outlet opening 20, and a fan inlet duct 21 isarranged as indicated. Thus, with the doors closed operation of the fanwill cause a circulation from the chamber 13 to the chamber A by way ofthe shelves so that a drying medium will be directed downwards uponcarbon tissue mounted on ferrotype plates resting upon the shelves, theperforations insuring even distribution over the tissue sheets.

The partition 11 is provided with an open- .ing 22 by whichcommunication is had between the compartments A and C, and thecompartment C has communication with the duct ,21 by Way of an opening23 in the upper wall of the enclosure and a branch duct 24; wherebycommunication between the chamber A and the fan is had by the two pathsdescribed, one including the chamber C and each forming a by-pass forthe other.

Within the chamber C are arranged a number of coils 25 interspaced bybaffle plates 26 and having connection as by pipe 27 with a source ofrefrigerant with which the coils form a refrigerating unit.

' Within the branch duct 24 are coils 28 having connections as by pipe29 with a source of heating medium such as steam, the steam supply tothe coils 28 being conveniently controlled by a thermostatic valve 80actuated by a thermostatic unit 31 in the fan outlet duct 18, althoughit will be understood that the unit 31 might be located in the fan inletduct 21.

Operation of the apparatus in drying carbon tissue placed on the shelves2, access to which for the purpose is had through the door 15, will beevident. Operation of the fan 16 effects circulation and recirculationas already described causing a draft of air evenly downwards upon thetissue sheets and away therefrom in all directions. The pro-j portionsare preferably such that about 10% of this air passes through thechamber C. In the chamber C presuming the coils 25 actively refrigerant,this portion of the air is caused to drop its moisture as will beunderstood; and as this air subsequently passes over the heating coils28 it is again brought to the desired temperature, which I find to beabout 68 F., the proper heating coil temperature being maintained by thethermally responsive valve 30.

The portion of air thus conditioned is mixed in the fan 16 with thatportion of the circulating air by-passed around-the chamber 0 the tissuesheets being subjected to this mixture as will be well understood by onefamiliar with the air conditioning art; however, the whole of therecirculating air is substantially constantly maintained in the properconditions of temperature and humidity to produce a constant dryingefi'ect entirely independent of weather or other general atmosphericconditions.

What I claim is:

1. Apparatus of the. character described and comprising means forsupporting plates to be dried, means for directing a drying medium uponsaid lates, means arranged about said parts to ormva drying chamberwithin which the parts are located, means providing a second chamber,said directin means having supply connectionwith sai second chamber,means providin a third chamber communicating with said rst chamber,refrigerant means having a cooling surface in said third chamber, meanseifecting circulation from said first. and third chambers to said secondchamber and hence from the second to the first chamber through saiddirecting means, and heatin means ar-' ranged 1n the flow of circulationfrom the third to the second chamber.

2. Apparatus of the character described and including a plurality ofshelves each adapted to support a ferrotype plate bearing a sheet oftissue, said shelves being hollow and perforate each on one side, and

their hollows having connection with a source of drying medium, thearrangement being such that said medium will be directed from a shelfand against the tissue on the 1 adjacent shelf.

3. Apparatus of the character described and including a rack of shelveseach adapted to support a ferrotype plate bearing a sheet of tissue,said shelves being hollow and perforate each on one side, and havingconnection with a source of drying medium, the

arrangement being such that said medium will be directed vertically froma shelf and against the tissue on the adjacent shelf, an enclosure forsaid rack, means for conditioning said medium, and means for circulatingthe same through said conditioning means, said shelves and saidenclosure.l

4. Apparatus of the character described and including a rack of shelveseach adapted to support a ferrotype plate bearing a sheet of tissue,said shelves being hollow and perforate each on one side and havingconnection with a source of drying medium, the arrangement being suchthat said mediun'iwill be directed vertically from a shelf andagainstthe tissue on the adjacent shelf,

- an enclosure for said'rack and having walls spaced from said shelveswhereby said medium may find 'exit from between the shelves on all sidesthereof, means for conditioning said medium, and means for circulatingthe same through said conditioning means, said shelves and saidenclosure,

5. Apparatus of the character described and including a rack of shelveseach adapted

